If they lay better for you when you give them just a bit more protein, then that's what I'd do. Actually, that is what I do and it makes a difference, especially with my older layers. You could also switch to a feed with a bit more protein, like a gamebird or flockraiser feed. Some areas even carry a layer feed with a little higher percentage of protein. Otherwise, you can keep doing what you're doing and just give them a bit more protein on the side. If you feed any non-layer feed, you should provide oyster shell for calcium.
You might want to look at some of the older threads on how to help your chickens deal with hot weather, if you haven't already. I know the heat can be brutal on them, even when you're doing everything you can. It got up to 113-114 degrees the first summer I lived in a small town not too far from Dallas.
Things like more shade, fans, shallow water to wade in and ice in their water can help cool them down. Feeding treats like frozen melon can help, too. I even started adding ice to my chickens' water during a heat wave this summer, for the first time in a long time, since they were showing signs of stress from the heat. You can't have too much ventilation in the coop when it's hot and it helps the coop cool off faster at night. This gives them a longer period of time at night with less heat stress.
When the time comes that you want to get more chickens, I'd look at some of the breeds that are know for being particularly heat tolerant, too. Henderson's breed chart is good.
http://www.ithaca.edu/staff/jhenderson/chooks/chooks.html
Your 5 chickens should be able to provide you 3 eggs a day for quite awhile, when they're laying well. When the weather is hot, though, it does stop some chickens from laying. So can a fall molt. Some chickens lay okay in the winter without supplemental lighting and you're far enough south that you have a longer day length. Winter laying might not be an issue for your flock at all. You might not have enough eggs during certain times of the year when it's very hot or they're molting.
Promptly refrigerated clean eggs, with the bloom on, lasted up to 6 months, when Mother Earth News did a trial of different preservation methods for eggs. You can hold back a few more of the extra eggs in the refrigerator just before you go into the worst heat of summer, to tide you over. You could also get more chickens that are heat tolerant, if you think it's going to be a problem next year.
